1. Field of the Invention
The invention relates to a refrigerant composition for use in a compressor-type refrigerating apparatus. Specifically, the invention relates to refrigerants containing HFC compounds in place of environmentally-harmful chlorinated flourocarbons.
2. Description of the Prior Art
Conventional commercially-available refrigerants typically comprise a mixture of various components including one or more fluorocarbons. Such refrigerants are widely used as refrigerants in air conditioning systems, refrigerators and other heat pump applications. Conventional heat pumps operate on a principal of cyclic compression and decompression of the refrigerant, which may undergo a phase conversation between liquid and gas. Heat is absorbed or removed from a space by changing the refrigerant from a liquid to a gas or otherwise reducing the pressure of the refrigerant. The refrigerant is then compressed within a compressor, which significantly raises the pressure of the vapour. The high pressure vapor is conveyed to a condenser, and undergoes a heat exchange with a cooler medium such as the surrounding air. The release of heat energy to the surrounding air causes the refrigerant to drop in temperature and condense to a liquid. The cooled liquid refrigerant is transmitted back to the cool side, and passed through an expansion valve which lowers the pressure of the liquid causing the liquid vaporize by absorbing heat energy from the surrounding air, thus commencing the cycle again.
It has been found that certain refrigerants possess good qualities for use with such a system, owning to their ability to undergo a phase change at or near the temperatures usually found at the warm and cool sides of the heat pump, under pressures readily obtainable by an inexpensive compressor. Until recently, chlorofluorocarbons were in widespread use, either in the form of a single compound or isotropic mixtures containing one or more chlorofluorocarbons (CFCs). In recent years, environmental considerations have placed severe restrictions on the use of CFCs, as these have been found to cause damage to the earth""s ozone layer. In response to this challenge, alternative refrigerants were developed containing hydrofluorocarbons (xe2x80x9cHFCxe2x80x9d) refrigerants, thus avoiding the use of environmentally-harmful chlorinated compounds. The prior art discloses various multi-component HFC mixtures. By way of several representative examples:
U.S. Pat. No. 6,035,648 to Hickman et al. discloses a refrigerant mixture consisting of R-32, R-125 and R-134a in the approximate ratio of 25/25/50. A different mixture of the same three components is disclosed in U.S. Pat. No. 5,736,063, to Richard et al. This reference also discloses two component mixtures, and mixtures containing propane as a component, as well as carbon dioxide. U.S. Pat. No. 5,709,092 to Shiflett discloses a mixture of the same three components, in the range of 5-59% HFC 125; 5-59% HFC 32; and 5-35% HFC 134 or 134a. Propane also is disclosed as an additional component. A mixture of the same three components is disclosed in U.S. Pat. No. 5,647,224, to Kushiro et al.
Desirably, a refrigerant should be chemically stable, possessed of low toxicity and suitable for use in a mechanical system in which the refrigerant is exposed to lubricants and metals, without causing corrosion or excessive lubricant degradation.
In a further aspect, a refrigerant should be miscible with the lubricants used in a variety of refrigerating devices. Conventional CFC-free refrigerants are not suitable for use in a range of refrigerating devices but rather they typically are formulated to work in a single type of device. Since many refrigerating devices employ mineral oil as a lubricant, the refrigerant should be miscible with this lubricant. Conventional HFC refrigerants tend to be not miscible or easily miscible with mineral oil and are thus not suitable for such uses. It is desirable to provide a CFC-free refrigerant suitable for use in a number of different types of refrigerating devices, in order to simplify fabrication and maintenance of a variety of such devices.
The present invention comprises a mixture of three HFC refrigerants components, along with an alcohol. The alcohol must have a suitable critical temperature which is compatible with the use of the refrigerant. Preferrably a lower alkyl or branched alkyl alcohol including methanol or ethanol. The most preferred is ethanol, preferably anhydrous ethanol. The function of the alcohol is to improve miscibility with lubricants typically found in refrigerating devices, in particular mineral oils of the type used in the mechanical components of existing R22 based refrigerating systems. The three HFC components are HFC 32, HFC 125 and HFC 134a. Optionally, the mixture includes a fifth component, namely a lower alkyl hydrocarbon such as R290 (propane) or isobutane. The refrigerant of the present invention is formulated into a composition compatible with and suitable for use in at least one conventional refrigerating device and preferrably several such devices, i.e. having a vapour pressure or critical temperature which is similar to that of conventional refrigerating devices.
Without wishing to be restricted to any theory, it is believed that the addition of the alcohol component enhances the performance of the composition by altering the viscosity of the oil that becomes entrained within the refrigerant during operation of the refrigerating device.
The composition of the present invention comprises HFC 32 in the amount of about 20% to 25% by weight; HFC 125 in the amount of about 22% to 28% by weight; HFC 134a in the amount of about 48% to 54% by weight; and a lower alkyl alcohol in the amount of about 0.08 to 1% by weight.
In one aspect, the invention is a refrigerant composition comprising HFC 32 from about 22% to 24% by weight; HFC 125 in the amount of about 24 to 26 by weight and HFC 134a, in the amount of about 49% to 53.3% by weight; and lower alkyl alcohol in the amount of about 0.6% to 0.8% by weight.
In one aspect, the refrigerant comprises the following formulation:
In a still more preferred embodiment, the mixture comprises HFC 32 at about 23% by weight; HFC 125 at about 25% by weight, HFC 134a at about 51.3% by weight and ethanol in the amount of about 0.7% by weight.
Optionally, an additional component is added to the mixture, namely a lower alkyl hydrocarbon in the amount of between 0% and 4.0% by weight. xe2x80x9cLower alkylxe2x80x9d means a straight or branched chain C1-C6 with a preferred species being isobutane propane with propane being most preferred. Suitable alkyls are those which exist in the gas phase at room temperature and atmospheric pressure. Another suitable lower alkyl is isobutane.
The term xe2x80x9caboutxe2x80x9d used herein means a variation of xc2x10.1 from the expressed percentages.